Dementia Due to Huntington’s Disease

Dementia Due to Huntington’s Disease

Dementia is also a characteristic of Huntington’s disease, an au-tosomal dominant inheritable condition localized to chromosome 4. Unfortunately, this condition does not become apparent until age 35 to 45 years, usually after childbearing has occurred. Fifty percent of offspring are affected. There is also a juvenile form of the disease. Huntington’s disease affects about four in 100 000 people, making it a significant cause of dementia in middle-aged adults.

The pathology of Huntington’s disease involves selective destruction in the caudate and putamen. In the caudate nuclei, GABA concentrations are reduced to 50% of normal. The fron-tal lobes of the cerebral cortex are also involved, but GABA and choline acetyltransferase concentrations in the cortex are normal.

The most noticeable clinical feature of Huntington’s dis-ease is the movement disorder, which involves both choreiform movements (frequent movements that cause a jerking motion of the body) and athetosis (slow writhing movements). In the juve-nile form of Huntington’s disease, which represents about 3% of all cases, the chorea is replaced by dystonia, akinesia and rigidity, and the course of the disease is more rapid than in the adult form. In the early stages of the disease, the chorea is not as noticeable and may be disguised by the patient by making the movements seem purposeful.

The dementia typically begins 1 year before or 1 year af-ter the chorea and, unlike patients with other dementias, patients with Huntington’s disease are often well aware of their deterio-rating mentation. This may be a factor in the high rates of suicide and alcoholism associated with this condition. Although attempts have been made to increase ACh and GABA concentrations in these patients, such pharmacological interventions have been un-successful, and the dementia in untreatable. Genetic counseling is indicated.